A radio access method and a radio network (hereinafter, referred to as Long-Term Evolution (LTE) or Evolved Universal Terrestrial Radio Access (EUTRA)) of cellular mobile communication have been examined in the Third Generation Partnership Project (3GPP). In LTE, an orthogonal frequency division multiplexing (OFDM) method is used as a downlink communication method. In LTE, a single-carrier frequency division multiple access (SC-FDMA) method is used as an uplink communication method. In LTE, a base station apparatus is also referred to as evolved NodeB (eNodeB), and a mobile station apparatus is also referred to as user equipment (UE). LTE is a cellular communication system in which a plurality of areas covered by a base station apparatus are allocated in a cell form. A single base station apparatus may manage a plurality of cells.
LTE corresponds to time division duplex (TDD). LTE employing the TDD is also referred to as TD-LTE or LTE TDD. The TDD is a technique which can realize full-duplex communication in a single frequency band through time division multiplexing of an uplink signal and a downlink signal.
In 3GPP, it has been examined that a traffic adaptation technique and an interference reduction technique (DL-UL interference management and traffic adaptation) in which a ratio of an uplink resource and a downlink resource is changed depending on uplink traffic and downlink traffic are applied to the TD-LTE.
In NPL 1, a method of using a flexible subframe is proposed as a method of realizing traffic adaptation. A base station apparatus can receive an uplink signal or transmit a downlink signal in a flexible subframe. In NPL 1, a mobile station apparatus regards the flexible subframe as a downlink subframe unless the mobile station apparatus is instructed to transmit an uplink signal in the flexible subframe by the base station apparatus. The traffic adaptation technique is also referred to as dynamic TDD.
NPL 1 discloses that a hybrid automatic repeat request (HARQ) timing for a physical downlink shared channel (PDSCH) is determined on the basis of an uplink-downlink configuration which is newly introduced, and that HARQ timing of a physical uplink shared channel (PUSCH) is determined on the basis of the initial UL-DL configuration.
NPL 2 discloses that (a) a UL/DL reference configuration is introduced, and (b) several subframes may be scheduled to be used for either an uplink or a downlink through dynamic grant/assignment from a scheduler.